Story highlights

Trump holds up North Korea test as evidence of Clinton's "failure" as secretary of state

Clinton says US will not allow Pyongyang to develop the means to deliver nuclear weapons

Washington (CNN)Within hours of North Korea's nuclear test Friday, it had become a political weapon in the US.

The test -- Pyongyang's fifth and most powerful -- had enough force to "rip the heart out of a city," one expert said. It marks one more step in North Korea's efforts to develop the missiles and miniaturized warheads needed to reach its perceived enemies. And it raises the possibility that if North Korea succeeds, it will look for black market buyers for its lethal goods.

Republican presidential candidate Donald Trump seized on the test to discredit his Democratic rival Hillary Clinton, arguing that "it's just one more massive failure from a failed secretary of state."

Clinton avoided commenting on Trump's North Korea positions in remarks Friday. Instead, after meeting with foreign policy experts in New York, she called for cranking up sanctions on North Korea, pushing China to do more, and drew a line in the sand.

"We are not going to let North Korea pursue a nuclear weapon with the ballistic missile capacity to deliver it to United States territory," Clinton said. "That is absolutely a bottom line."

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Analysts say the internal logic driving North Korea's leadership means the standard international response to the nuclear tests -- denouncements, international meetings, possibly new sanctions -- will likely fail once again. And they say that it won't be long before a President Clinton or President Trump is forced to confront the issue and its impact on Asia.

"This administration is handing over what's shaping up to be the number one national security problem for the next administration, whether it's Clinton or Trump," said Victor Cha, Korea chair at the Center for Strategic and International Studies.

Beyond the lethal improvements to a nuclear arsenal that's already estimated to include a stockpile of 15 to 20 weapons, analysts say North Korea could sell the technology and bombs to terrorists. In the past, North Korea has sold missiles to Pakistan and Iran, it tried to sell to Iraq's Saddam Hussein, and supplied Syria with a nuclear reactor that Israel promptly bombed.

Clinton flagged the terrorism concern in New York Friday.

"ISIS and North Korea are not entirely unconnected because the greatest threat of all would be terrorists getting hands on loose nuclear material," Clinton said, "so it's vital we bring the world together to stop North Korea's dangerous game."

Cha says data that CSIS has collected make it clear the 45th US president will be dealing with Pyongyang sooner rather than later.

"You can be certain they will do something when the next president comes in," Cha said. "There's a window before and after US presidential elections where they've done things before, so they'll be putting themselves front and center and neither candidate has really said much about what they'll do."

Trump laid out a position on North Korea as early as 1999 in a Wall Street Journal op-ed titled, "America Needs a President Like Me." In that piece, he said he'd bomb North Korea if it didn't give up its nuclear ambitions.

"I would let Pyongyang know in no uncertain terms that it can either get out of the nuclear arms race or expect a rebuke similar to the one Ronald Reagan delivered to Muammar Ghaddafi in 1986," when the US president launched airstrikes against Libya for sponsoring terrorism, Trump wrote.

More recently, after the North Korean nuclear test in January, Trump said the US should pressure China -- Pyongyang's closest ally -- to rein in its close ally because it has "total control" over its neighbor. If it doesn't, Trump said, "We should make trade very difficult with China."

In February, he appeared to suggest the assassination of North Korean president Kim Jong Un, telling "CBS This Morning" that he "would get China to make that guy disappear in one form or another very quickly."

Then, in a May interview with Reuters, he said he would be willing to meet with the North Korean leader.

Trump has also proposed withdrawing some US troops from Asia and has said that Japan and South Korea, two strong US allies, should develop their own nuclear capabilities to deal with North Korea, rather than continue to rely on the US to protect them.

That proposal, analysts and administration officials point out, would mean dispensing with the US security umbrella that has been key to stability in Asia since the end of World War II.

Others say that starting a trade war with China would cause ripples of economic damage across the world, not least in the US. And a meeting between a sitting US president and a North Korean leader would be a radical departure from established practice and policy.

"Trump has said all kinds of things, no one really knows what he means," Cha said. The Trump campaign did not respond to requests for comment.

Clinton, meanwhile, has her own problem areas to address.

While she was secretary of state, North Korea broke off international talks aimed at ending its nuclear program and violated UN bans on testing long-range missiles and nuclear weapons.

Friday in New York, she called for a "rethinking of the strategy" and, in an area of agreement with Trump, pushed an urgent effort to convince China to rein North Korea in.

China generally opposes sanctions, saying they're counterproductive, and has enforced them in lackluster fashion. China's leaders, obsessed with stability, are deeply concerned about the impact if North Korea collapsed, and Chinese towns along the border are also economically dependent on trade with North Korea.

But Beijing has been increasingly frustrated with North Korea's young leader, creating gaps between the two that haven't existed before, analysts say.

Clinton said Friday she thinks "we have an opening here that we haven't had for the last several years that I intend to do everything I can to take advantage of."

She also said she thinks there's a role for more sanctions.

That's a position that Republicans also take. Since North Korea first conducted a nuclear test in 2006, international sanctions have focused largely on its weapons.

In March, the United Nations passed the first set of sanctions that went further, banning all weapons trade; requiring the inspection of all cargo leaving and entering the country; expanding the number of individuals being sanctioned; requiring countries to expel North Korean diplomats accused of illicit activities, and prohibiting the import of luxury goods such as Jet Skis and watches.

There's still room to pressure North Korea further, as Clinton, along with Republicans such as California Rep. Ed Royce, the chairman of the House Foreign Affairs Committee, suggest.

An act passed by Congress gives the administration the power to sanction non-North Korean entities acting as an agent for the country -- in other words, Chinese companies and financial institutions. "We have a lot of leverage," Clinton said Friday, "and we are going to exercise that leverage."

President Barack Obama said in a statement Friday that the US would pursue new sanctions at the UN along with its allies. So far, though, "the Obama administration still hasn't sanctioned a single Chinese entity on secondary sanctions," said Bruce Klingner, a senior research fellow for Northeast Asia at the Heritage Foundation.

In a January 2015 executive order, the administration also gave itself the authority to sanction any North Korea entity for simply being a North Korean entity.

"The administration has barely scratched the surface when it comes to using all of the tools at its disposal to push back against" North Korean illicit behavior, said Tennessee Republican Sen. Bob Corker, chairman of the Senate Foreign Relations Committee.

With assistance from Dan Merica in New York and Jeremy Diamond in Washington.